Extensible ladder



D MORROW July 9, 1957 EXTENSIBLE LADDER 2 Sheets-Sheet 1 Filed Oct. 23, 1951 FIG. 1

y 19'57 'D. MORROW 2,798,653

EXTENSlBLE LADDER Filed Oct. 23. 1951 2 Sheets-Shasta 2 INVENTOR. Dav/0 MORROW W 91mm Unie 2,798,653 Patented July 9, 1957 EXTENSIBLE LADDER David Morrow, Silver Spring, Md., assignor to Fair-child Engine and Airplane Corporation, Hagerstown, Md, a corporation of Maryland Application October 23, 1951, Serial No. 252,688

6 Claims. (Cl. 228-191) This invention relates to extensible ladders, and has particular reference to ladders of lazy tongs construction which may be folded into a compact unit for easy stowage when not in use.

The ladder of the present invention was devised to facilitate entry and exit of personnel from an elevated aircraft cabin and has proved to be admirably adapted for that purpose, although its utility is not so limited. The ladder is extendedfrom collapsed or contracted condition in which it is stowed in the cabin or fuselage, and lowered to the ground when exit from the cabin is desired and is extended and elevated to the cabin when entry thereto is desired, thus solving a problem not otherwise susceptible of solution with non-stowable fixed ladders or unstable rope ladders which are not attachable or detachable from the remote end thereof.

The extensible ladder of this invention comprises side members, each. of which consists essentially of a primary lazy tong, structure and secondary lazy tong structure superimposedthereon to brace and strengthenthe former, these. side members being spaced in parallel relation by rungs. which lie in close proximity when the ladder is collapsed and are spaced at regular intervals vertically when the ladder isextended. Secured to the upper end of the ladder are one or more. hooks for attaching the ladder to the point which is to be reached thereby. Preferably, the hook is an extension of one of the crossed bars of the side member and has a ball-like head or knob adapted to be inserted in a key hole slot in the structure intended to be sealed with the ladder, such as the hatch of an aircraft cabin, its outer surface, or the surface of a large tail fin or rudder, as examples. Means also may be providedfor locking the ladder in extended position, such as alower mounting hook or knob cooperating with a corresponding lower key hole slot, or means for locking the lazy tong side members against collapsing when extended.

It will be seen that the collapsible ladder of this invention forms a strong and rigid structure when extended and may be handled from either end and secured safely to the object to be scaled, while being capable of being retracted or collapsed from either end for compact stowage.

For amore complete understanding of the invention, reference may be had to the accompanying drawings, in which:

Figure 1 is an edge view of the ladder of this invention in extended position;

Fig. 2 is a front view thereof;

Fig. 3 is a schematic edge view of the ladder in semiextended position;

Fig. 4 shows the ladder in collapsed position ready for stowage;

Fig. 5 is an enlarged fragment of a side wall having a key hole slot for receiving the knob hook of the ladder; and

Fig. 6 illustrates one way of locking the ladder in semiextended position for use in ascending a vertical tail fin or rudder of large aircraft provided with the key hole slots of Fig. 5 for receiving mounting knobs or hooks at both ends of the ladder.

Referring to Figs. 1, 2 and 3 of the drawings, numeral 10 designates the side members, each of which comprises a primary lazy tong 11, shown in heavy lines in Fig. 3, and a secondary lazy tong 12, shown in dotted lines in Fig. 3.

The primary lazy tong 11 comprises a plurality of crossed bars 13 of light-weight metal, such as alloy steel, preferably channelor box-shaped in cross-section and pivoted at their center points on the reduced ends 14 of the corresponding rung 15, which preferably is tubular, although it may be a fiat step extending in the common plane of corresponding opposite crossed bars 13, so as to lie horizontally when theladder is inclined like a staircase. The rung end extension 14 may be pinned to the inner crossed bar 13 and the outer crossed bar 13 is secured thereto by a nut 16 recessed within the channelor box-section of that crossed bar, as shown in Figs. 1 and 2. The free ends of the adjacent crossed bars 13 are pivoted together by bolts 17, also as shown in Figs. 1 and 2'.

As many such sets of crossed bars are secured together in that way as the extended length of the ladder may require, and: the upper; and lower free ends of the crossed bars 13 are connected by half length bars 13 and 13", respectively, the free ends of which are pivoted together on the respective upper andlower rungs 15 and 15".

The lower rung 15" preferably is provided with buffer rings 18 which are of larger diameter thanthe rung 15" so that they reston the ground or other supporting surface, rather than the rung 15" or the ends of the lower crossed bars 13, whereby the latter arev prevented from being injured by contact with the ground.

Superimposed on the primary lazy tong structure 11 just described, isthe secondary lazy tong structure 12, shown in dotted lines in Fig. 3, and constructed essentially the same way except that it is not fitted with rungs or upper and lower half crossed bars like 13' and 13". Thus, secondary CI'OSSCd QbaIS 19 are pivoted together at their center pointson bolts 20 and at their free ends to the free ends of the adjacent set, about bolts 21, with the free ends; of the uppermost and, lowermost secondary crossed bars 19 being pivoted at the midpoints 21 of upper and lower primary crossed bars 13'. If desired, or the rung spacing requiresit, rungs like 15 may also extend between pivot points 20 on secondary structure 12, or between corresponding opposite points on either or both the primary and secondary structures: 11, 12.

In addition to being pivoted at its extreme ends 21' to the primary lazy tong structure 11, the secondary lazy tong structure 12 ispivoted thereto by pivot bolts 22 at the pointswhere the-primary bars 13 cross the secondary bars 19, which is the first and third quarter points of each, as is shown particularly in Fig. 3. Thus, the primary and secondary lazy tong structures 11 and 12 are pivoted together and. jointly constitute the side member at each side of the ladder thus formed, whereby they supplement the strength and brace each other. Notwithstanding this double structure, the ladder may be collapsed into the compact package shown in Fig. 4, which is readily stowable in a small space within aircraft or elsewhere.

Mounting means for the ladder preferably take the form of one or more knob-like hooks such as that designated 23 and comprising a spherical enlargement on an extension 24 of the outer end of one of the upper primary cross bars 13'. The extension 24 preferably is of reduced diameter and circular in cross-section, and is curved upwardly so as to extend substantially horizontally when the ladder is fully extended. Similarly, the free end of the corresponding primary crossed bar 13 which lies parallel to the hooked upper crossed bar 13, is provided with an 3 integral knobbed hook 25 whose reduced shank 26 also is so curved as to extend substantially horizontally when the ladder is fully extended.

, The surface of the structure to be scaled with the collapsible ladder of-this invention is provided with a key hole-shaped slot 27 such as is shown in Fig. 5, where a thin wall, likea sheet metal aircraft skin is depicted by wayof example. Assuming that the key hole slot 27 is formed high in a vertical wall of a sheet metal structure like the tail fin or rudder 28 of a large airplane, as shown in Fig. 6, for example, the ladder is extended and the upper knob 23 inserted in the circular hole 29 of the key hole slot 27. When the ladder is released, the reduced shank 24 drops into the narrow portion or slit 30 of the key hole slot 27, and the upper end of the ladder is secured.

Where the lower end of the ladder may not rest on a suitable supporting surface, a lower key hole slot may be preferably provided in the wall of the structure 28 for the reception of the lower knobbed book 25. It will be seen that the lower hook 25 not only looks the ladder at its lower end, but also determines its extended length, in a manner readily understood, and as seen in Fig. 6.

In cases where the entry or batch is on an elevated platform or floor, such as the under surface of a cabin, crew compartment or fuselage of an aircraft, for example, the securing hook 31 is mounted at the upper end of each side member of the ladder, with its shank 32 extending substantially at right angles thereto, as shown in Figs. 1 and 3. In that case, the key hole slot is positioned vertically as before, although it may be simply a narrow vertical slot like 30 in Fig. 5, cut in the upper edge of coaming surrounding the hatch or the like.

Operation of the collapsible ladder of this invention will be readily understood from the foregoing description of its structureand, although a preferred embodiment thereof has been described, the invention is not limited thereby except to the extent provided by the scope of the appended claims.

I claim:

1. In a collapsible ladder, the combination of a pair of opposite spaced side members each comprising a lazy tong structure of a pair of crossed bars pivoted together at their center points and pivoted at their ends to adjacent pairs of crossed bars at the ends thereof, rungs extending between corresponding points on the opposite side members, and an extension terminating in a knob serving as mounting means on crossed bars near each end of the ladder, whereby each end of the ladder may be attached to a structure with the rungs of the ladder spaced apart from the respective structures.

2. In a collapsible ladder, the combination of a pair of opposite spaced side members each comprising a lazy tong structure of a pair of crossed bars pivoted together at their center points and pivoted at their ends to axlja cent pairs of crossed bars at the ends thereof, rungs extending between corresponding points on the opposite side members, an extension on at least one of said crossed bars in proximity to the uppermost ring, a knob on the extremity of said extension adapted to lodge in a slot in the structure to which the ladder is to be attached, whereby the said uppermost rung is spaced in proximity to the from the structure, as when the ladder is used to climb a a structure, as when the ladder is used to attain an elevated platform, another extension on at least one of said crossed bars more remote from the uppermost rung, and a knob on the extremity of said extension adapted to lodge in a slot in the structure to be attained with the use of the ladder, whereby the said uppermost rung is spaced apart wall.

3. In combination with an elevated element having a key hole slot therein, a collapsible ladder comprising lazy tong side members connected by spaced rungs, and at least a pair of knob-like extensions at the upper end of each of said side members, one of said knob-like extensions being closer to the uppermost rung than the other, the one being used when the uppermost rung is to be spaced in proximity to the elevated element, and the other being used when the upper rungs are to be spaced apart from the elevated element for insertion in said key hole slot when the ladder is extended.

4. In combination with an elevated element having a hole therein and a second hole below said first hole, a collapsible ladder comprising lazy tong side members connected by spaced rungs, and a hook-like extension at the upper and lower ends of said side members for insertion in said holes when the ladder is extended, whereby the ladder may be attached to said elevated element with the rungs spaced apart from said elevated element.

5. In combination with a wall of relatively thin material having vertically spaced pairs of holes therein, a collapsible ladder comprising lazy tong side members connected by spaced rungs, and a pair of hook-like extensions at the upper and lower ends of said structures for insertion in corresponding pairs of holes in'said wall to hold the ladder in extended position with the rungs spaced apart from said wall.

6. In combination with a wall of relatively thin material having vertically spaced pairs of key hole slots therein, a collapsible ladder comprising lazy tong side members connected by spaced'rungs, and a pair of knob-like extensions at the upper and lower ends of said structures for insertion in corresponding pairs of key hole slots in said wall to hold the ladder in extended position with the rungs spaced apart from the wall.

References Cited in the file of this patent UNITED STATES PATENTS 502,485 Dederick Aug. 1, 1893 663,883 Gregory Dec. 18, 1900 698,272 Glover Apr. 22, 1902 874,801 Siems et a1. Dec. 24, 1907 942,683 Vaghi Dec. 7, 1909 1,141,554 Klumpp June 1, 1915 1,626,145 Mitchell Apr. 26, 1927 1,837,585 Redinbaugh Dec. 22, 1931 2,182,277 Boor Dec. 5, 1939 2,246,457 Schultz June 17, 1941 2,367,253 Williams Jan. 16, 1945 2,396,034 Baker Mar. 5, 1946 FOREIGN PATENTS 22,271 Austria July 1, 1905 

